76 SOIL BACTERIOLOGY 



2. Treat as follows: 



(a) Control. 



(&) Add i per cent, of sugar. 



(c) Add i per cent, of green clover. 



3. Bring the moisture content of the soil up to two- thirds 

 saturation. 



4. Insert one round filter-paper, diameter smaller than 

 that of the flask, into each culture. Partially cover the 

 filter-paper with soil. 



5. Incubate at 28 C. 



6. At weekly intervals examine. Note the change in the 

 filter-paper. 



Exercise 3 

 Fermentation of Cellulose in Soil 



1. Prepare four large soup plates with 500 grams each of 

 soil. Use two plates of field and two plates of garden 

 soil. 



2. Add to each plate 5 grams of dry filter-paper cut into 

 strips about 2 inches long and J inch wide. These should 

 be thoroughly mixed with the soil and a little more water 

 than necessary for half -saturation added. 



3. In order to avoid rapid evaporation cover with inverted 

 plates and keep the moisture constant. 



4. After six to eight weeks remove the remaining paper 

 from the soil by passing the soil through a fine mesh sieve. 

 Now wash the paper, dry, and weigh. Although this 

 procedure does not always give uniform results, it will 

 show the relative cellulose-destroying power of the soil. 



